Women who gain weight throughout adulthood are at higher risk for developing breast cancer after menopause and women who lose weight may decrease their risk. Fifty percent of the Black female population is obese and overall breast cancer mortality is higher for Black women compared to White women. We propose the Obesity Reduction Black Intervention Trial (ORBIT), which builds on the findings of "Breast Cancer Risk Reduction in African-American Women" which showed significant weight loss, reduced dietary fat, and increased physical activity in the intervention compared to the control group. The next critical step in our research is to assess the efficacy of an adequately powered, theoretically driven, weight loss and maintenance intervention Two-hundred obese 30-65 year old Black women will be randomized to a 24-week treatment intervention or a 24-week control intervention. Participants in the treatment intervention will then participate in a 1-year maintenance intervention and the control participants will participate in a 1-year control intervention. Aims of the study include: 1) To estimate the effectiveness of a 24-week treatment intervention and 1-year maintenance intervention to produce and maintain weight loss; 2) To estimate the effectiveness 24-week treatment intervention and 1-year maintenance intervention to produce and maintain a reduction in total calories, total fat, and an increase in fiber and fruit and vegetable intake; 3) To estimate the effectiveness of a 24-week treatment intervention and 1-year maintenance intervention to produce and maintain an increase in physical activity; and 4) To estimate the effectiveness of a 24-week treatment intervention and 1-year maintenance intervention to produce and maintain changes in attitudes, self-efficacy, and social support related to diet, physical activity, and weight loss. The theoretical rationale for the aims, development of the interventions, and methodology are based on Social Cognitive Theory (SCT).